Pro-deal MPs try to force Johnson to seek EU customs union

Boris Johnson could see his Brexit legislation amended to require him to negotiate a customs union with the EU, after at least five pro-deal MPs said they would support this option.

The MPs – two former Conservatives, Nick Boles and Ken Clarke, plus at least three pro-deal Labour MPs, Melanie Onn, Gareth Snell and Ruth Smeeth – have put their names to a measure giving the government a mandate to negotiate a customs union.

The amendment to the Brexit bill would not change the UK’s proposed treaty with the EU, so Johnson has the option of accepting the amendment and then going into an election arguing to overturn it.

However, two Tory insiders told the Guardian it would be extremely difficult for Johnson and his Eurosceptic hardliners to accept any mandate for a customs union and it would be more likely for him to pull the bill and seek a general election.

Johnson’s chances of passing the EU withdrawal agreement bill through the House of Commons are on a knife-edge.

If at least five pro-deal MPs vote for it, then the chances of a customs union amendment passing later this week look fairly high. However, it could hinge on the actions of a handful of independents and the Democratic Unionist party, as well as the Liberal Democrats and SNP who have historically voted for remain and second referendum options rather than soft Brexit ones.

Labour has said it will back an amendment in favour of a customs union and accepts that one proposed by backbenchers has the best chance of cross-party success.

No 10 said Johnson would not accept a customs union. Robert Jenrick, the communities secretary, told the BBC now was not the time to discuss Britain’s future trading relationship with the EU and matters such as the customs union.

“This is a piece of legislation which simply puts into effect in UK law what the prime minister has managed to negotiate. The critical thing is the future relationship will be subject to a negotiating mandate that will be debated and voted on in the House of Commons,” he said.

“Those MPs who have concerns about issues such as that [the burden on businesses sending goods to Northern Ireland] or the customs union … they will have the ability to discuss and vote on that later on, once we have left the European Union.’

Jenrick added: “Those MPs who want to deliver Brexit will be voting with the government today.”